The focus will be on Jenny Watson, the head of the Electoral Commission, when she announces the result of the AV referendum on Friday.

Counting will not start until 4pm on Friday in 440 local voting areas – English councils, Scottish parliament constituencies, Welsh assembly constituencies and a single centre for Northern Ireland – and the results will be sent to 12 regional centres.

Watson will announce the results from each region, and then the final total, from the Excel centre in east London.

The turnout will be revealed before that, at about 3pm, giving the number of votes that either camp must achieve to take it over the winning 50% mark. Within a few hours, the result should be clear – although the final tally of votes may take all night.

For Watson, the referendum will be the biggest test of her stewardship since she was heavily criticised for failures on general election night, when hundreds of voters were shut out as queues built up outside poorly-manned polling stations.

That night, she was forced onto the airwaves to defend the commission's role in the problems. Her claim that she had no powers to direct returning officers in a general election was well founded but did not fall on sympathetic ears, and there were calls for her resignation.

Watson has overhauled the system since then. When the referendum legislation was being passed in parliament, she was given more powers to direct counting officers in referendums.

She has set out new guidance requiring every council to print enough ballot papers for its entire voting age population, regardless of turnout expectations.

Watson's last major outing was to announce the results of the referendum on new powers for the Welsh assembly, which she delivered in both English and Welsh with perfect pronunciation. She will be hoping the AV result goes as smoothly.